Coated nanotube surface signal probe

ABSTRACT

The coated nanotube surface signal probe constructed from a nanotube, a holder which holds the nanotube, a coating film fastening a base end portion of the nanotube to a surface of the holder by way of adhering the base end portion on the surface of holder in a range of a base end portion length with an electric contact state and covering a specified region including the base end portion with the coating film maintaining the electric contact state between the nanotube and the holder, a tip end portion of the nanotube being caused to protrude from the holder; and the tip end portion is used as a probe needle so as to scan surface signals. The coated nanotube surface signal probe can be used as a probe in AFM (Atomic Force Microscope), STM (Scanning Tunneling Microscope) other SPM (Scanning Probe Microscope).

This is a Divisional Application of application Ser. No. 10/326,472,filed on Dec. 20, 2002 now U.S. Pat. No. 6,800,865 which in turn is aDivisional Application Ser. No. 09/601,668, filed Aug. 3, 2000, now U.S.Pat. No. 6,528,785 issued Mar. 4, 2003, which is a 371 of PCT/JP9906359,filed Nov. 12, 1999, which is hereby incorporated in its entirety byreference.

TECHNICAL FIELD

The present invention relates to a surface signal operating probe for anelectronic device which uses a nanotube such as a carbon nanotube, BCNtype nanotube, BN type nanotube, etc. as a probe needle. Moreparticularly, the present invention relates to an electronic devicesurface signal operating probe which realizes a concrete method forfastening a nanotube to a holder, and which can be used as the probeneedle of a scanning probe microscope that picks up images of surfacesof samples by detecting physical or chemical actions on the samplesurfaces or as the input-output probe needle of a magnetic disk drive;and it further relates to a method for manufacturing such a probe.

BACKGROUND ART

Electron microscopes have been available in the past as microscopes forobserving sample surfaces at a high magnification. However, since anelectron beam will only travel through a vacuum, such microscopes havesuffered from various problems in terms of experimental techniques. Inrecent years, however, a microscopic technique known as a “scanningprobe microscope” has been developed which makes it possible to observesurfaces at the atomic level even in the atmosphere. In this microscope,when the probe needle at the tip end of the probe is caused to approachvery close to the sample surface at an atomic size, physical andchemical actions of the individual atoms of the sample can be detected,and an image of the sample surface can be developed from detectionsignals while the probe needle is scanned over the surface.

The first microscope of this type is a scanning tunnel microscope (alsoabbreviated to “STM”). Here, when a sharp probe needle located at thetip end is caused to approach to a distance at which the attractiveforce from the sample surface can be sensed, e.g., approximately 1 nm(attractive force region), a tunnel current flows between the atoms ofthe sample and the probe needle. Since there are indentations andprojections on the sample surface at the atomic level, the probe needleis scanned across the sample surface while being caused to approach andrecede from the sample surface so that the tunnel current remainsconstant. Since the approaching and receding signals from the probeneedle correspond to the indentations and projections in the samplesurface, this device can pick up an image of the sample surface at theatomic level. A weak point of this device is that the tip end of theprobe needle made of a conductive material must be sharpened in order toincrease the resolution.

The probe needle of an STM is formed by subjecting a wire material ofplatinum, platinum-iridium or tungsten, etc., to a sharpening treatment.Mechanical polishing methods and electrolytic polishing methods are usedfor this sharpening treatment. For example, in the case ofplatinum-iridium, a sharp sectional surface can be obtained merely bycutting the wire material with the nippers of a tool. However, not onlyis the reproducibility inaccurate, but the curvature radius of the tipend is large, i.e., around 100 nm, and such a curvature radius isinadequate for obtaining sharp atomic images of a sample surface withindentations and projections.

Electrolytic polishing is utilized for tungsten probe needles. FIG. 25is a schematic diagram of an electrolytic polishing apparatus. Aplatinum electrode 80 and a tungsten electrode 81, which constitutes theprobe needle, are connected to an AC power supply 82 and are suspendedin an aqueous solution of sodium nitrite 83. As current flows, thetungsten electrode 81 is gradually electrolyzed in the solution, so thatthe tip end of this electrode is finished into the form of a needle.When polishing is completed, the tip end is removed from the liquidsurface; as a result, a tungsten probe needle 84 of the type shown inFIG. 26 is completed. However, even in the case of this tungsten probeneedle, the curvature radius of the tip end is about 100 nm, andindentations and projects formed by a few atoms or more cannot besharply imaged.

The next-developed scanning type probe microscope is the atomic forcemicroscope (abbreviated as “AFM”). In the case of an STM, the probeneedle and sample must as a rule be conductors in order to cause theflow of the tunnel current. Accordingly, the AFM is to observe thesurfaces of non-conductive substances. In the case of this device, acantilever 85 of the type shown in FIG. 27 is used. The rear end of thiscantilever 85 is fastened to a substrate 86, and a pyramid-form probeneedle 87 is formed on the front end of the cantilever 85. A point part88 is formed on the tip end of the probe needle by a sharpeningtreatment. The substrate 86 is mounted on a scanning driving part. Whenthe point part is caused to approach the sample surface to a distance ofapproximately 0.3 nm from the sample surface, the point part receives arepulsive force from the atoms of the sample. When the probe needle isscanned along the sample surface in this state, the probe needle 87 iscaused to move upward and downward by the above-described repulsiveforce in accordance with the indentations and projections of thesurface. The cantilever 85 then bends in response to this in the mannerof a “lever”. This bending is detected by the deviation in the angle ofreflection of a laser beam directed onto the back surface of thecantilever, so that an image of the surface is developed.

FIG. 28 is a diagram of the process used to manufacture theabove-described probe needle by means of a semiconductor planartechnique. An oxide film 90 is formed on both surfaces of a siliconwafer 89, and a recess 91 is formed in one portion of this assembly bylithography and etching. This portion is also covered by an oxide film92. The oxide films 90 and 92 are converted into Si₃N₄ films 93 by anitrogen treatment; then, the entire undersurface and a portion of theupper surface are etched so that a cut part 94 is formed. Meanwhile, alarge recess 96 is formed in a glass 95, and this is anodically joinedto the surface of the Si₃N₄ film. Afterward, the glass part 97 is cut,and the silicon part 98 is removed by etching. Then, the desired probeneedle is finished by forming a metal film 99 used for laser reflection.Specifically, the cantilever 85, substrate 86, probe needle 87 and pointpart 88 are completed.

This planar technique is suited for mass production; however, the extentto which the point part 88 can be sharpened is a problem. In the finalanalysis, it is necessary either to sharply etch the tip end of therecess 91, or to sharpen the tip end of the probe needle 87 by etching.However, even in the case of such etching treatments, it has beendifficult to reduce the curvature radius of the tip end of the pointpart 88 to a value smaller than 10 nm. The indentations and projectionson the sample surface are at the atomic level, and it is necessary toreduce the curvature radius of the tip end of the point part 88 to avalue of 10 nm or less in order to obtain sharp images of theseindentations and projections. However, it has been impossible to achievesuch a reduction in the curvature radius using this technique.

If artificial polishing and planar techniques are useless, the questionof what to use for the probe needle, which is the deciding element ofthe probe, becomes an important problem. One approach is the use ofwhiskers (whisker crystals). Zinc oxide whiskers have actually beenutilized as probe needles. Whisker probe needles have a smaller tip endangle and tip end curvature than pyramid needles produced by planartechniques, and therefore produce sharper images. However, whiskermanufacturing methods have not been established, and the manufacture ofconductive whiskers for STM use has not yet been tried. Furthermore,whiskers with the desired cross-sectional diameter of 10 nm or less havenot yet been obtained.

Furthermore, such probe needles have suffered from many other problems:e.g., such probe needles are easily destroyed by strong contact with thesample surface, and such needles quickly become worn under ordinary useconditions, so that use becomes impossible.

In recent years, therefore, the idea of using carbon nanotubes as probeneedles has appeared. Since carbon nanotubes are conductive, they can beused in both AFM and STM. A carbon nanotube probe needle has beenproposed as a high-resolution probe for imaging biological systems in J.Am. Chem. Soc., Vol. 120 (1998), p. 603. However, the most importantpoints, i.e., the question of how to collect only carbon nanotubes froma carbon mixture, and the question of how to fasten carbon nanotubes toa holder, remain completely unsolved. In this reference as well, the useof an assembly in which a carbon nanotube is attached to a holder bymeans of inter-molecular force is mentioned only in passing.

Furthermore, besides carbon nanotubes, BCN type nanotubes and BN typenanotubes have also been developed as nanotubes. However methods ofutilizing such nanotubes have remained completely in the realm of theunknown.

On a different subject, memory devices have evolved from floppy diskdrives to hard disk drives, and further to high-density disk drives, asthe memory capacity of computers has increased in recent years. Asinformation is packed into smaller spaces at higher densities, the sizeper bit of information decreases; accordingly, a finer probe needle isalso required for input-output. In conventional magnet head devices, itis impossible to reduce the size of the probe needle beyond a certainfixed value, so that there are limits to the trend toward higherdensity.

As described above, systematic conventional techniques for sharpeningprobe needles are electrolytic polishing of metal wire materials andlithography and etching treatments of semiconductors. In the case ofthese treatments, however, the tip end curvature radius of the probeneedle can only be sharpened to about 100 nm; accordingly, it is verydifficult to obtain sharp images of indentations and projections formedby a few atoms or more on the sample surface. Furthermore, the degree ofsharpness obtained by mechanically cutting metal wire materials with atool such as nippers, etc. is also insufficient to capture sharp imagesof indentations and projections. The use of whiskers is still anuncertain technique, and the use of nanotube probe needles such ascarbon nanotubes, etc. has been a task for the future. Furthermore,conventional magnetic head devices have also approached their limit interms of size.

Accordingly, the object of the present invention is to provide theutilization of nanotubes with a small tip end curvature radius assurface signal operating probe needles and further to establish aconcrete structure for probes using nanotube probe needles, and a methodfor manufacturing the same. The present invention shows that suchnanotube probe needles are not easily destroyed even when they contactatomic-level projections during probe needle scanning, that such probeneedles can be firmly fastened to the holder so that the probe needlewill not come loose from the holder during such scanning, and that suchprobe needles can be inexpensively mass-produced. Furthermore, thepresent invention shows that samples that could not be observed withhigh resolution in the past can be clearly observed using the nanotubeprobe needles thus manufactured.

DISCLOSURE OF INVENTION

The present invention is to accomplish the above-described object. Thesurface signal operating probe for electronic devices of the presentinvention is characterized in that the probe comprises a nanotube, aholder which holds the nanotube, and a fastening means which fastens thebase end portion of the nanotube to the surface of the holder so thatthe tip end portion of the nanotube protrudes; and surface signals areoperated by the tip end portion of the nanotube that is used as a probeneedle.

The present invention provides a surface signal operating probe in whichthe fastening means is a coating film, and the nanotube is fastened tothe holder by covering a specified region of the nanotube including thebase end portion by means of the coating film.

Furthermore, the present invention provides a surface signal operatingprobe in which the fastening means is a fused part, and the base endportion of the nanotube is fusion-welded to the holder by this fusedpart.

The present invention provides a surface signal operating probe in whichthe above-described electronic device is a scanning probe microscope,and physical and chemical actions on the sample surface are detected bythe nanotube used as a probe needle. Such a scanning probe microscopeincludes scanning tunnel microscopes, atomic force microscopes, etc.

Furthermore, the present invention provides a surface signal operatingprobe in which the above-described electronic device is a magneticinformation processing device, and magnetic information is inputted ontoand outputted from a magnetic recording medium by the nanotube.

As a method for manufacturing this probe, the present invention providesa method for manufacturing an electronic device surface signal operatingprobe, and this method comprises a first process in which a voltage isapplied across electrodes in an electrophoretic solution in which ananotube that constitutes the probe needled is dispersed, so that thisnanotube is caused to adhere to the one of the electrodes for DC voltageor to both electrodes for AC voltage in a protruding fashion, a secondprocess in which the electrode to which the nanotube is attached in aprotruding fashion and a holder are caused to approach very closely toeach other, and the nanotube is transferred to the holder so that thebase end portion of the nanotube adheres to the holder surface in astate m which the tip end portion of the nanotube is caused to protrude,and a third process in which a specified region that includes at leastthe base end portion of the nanotube adhering to the holder surface issubjected to a coating treatment so that the nanotube is fastened to theholder by the resulting coating film.

Furthermore, the present invention provides a method for manufacturingan electronic device surface signal operating probe, and this methodcomprises a first process in which a voltage is applied acrosselectrodes in an electrophoretic solution in which a nanotube thatconstitutes the probe needled is dispersed, so that this nanotube iscaused to adhere to the electrodes in a protruding fashion, a secondprocess in which the electrode to which the nanotube is attached in aprotruding fashion and a holder are caused to approach very closely toeach other, so that the base end portion of the nanotube is caused toadhere to the holder surface in a state in which the tip end portion ofthe nanotube is caused to protrude, and a third process in which anelectric current is caused to flow between the nanotube and the holderso that the base end portion of the nanotube is fused to the holder.

In addition, the present invention provides a method for manufacturingan electronic device surface signal operating probe, and this methodcomprises a first process in which a voltage is applied acrosselectrodes in an electrophoretic solution in which a nanotube thatconstitutes the probe needled is dispersed, so that this nanotube iscaused to adhere to the electrodes in a protruding fashion, a secondprocess in which the electrode to which the nanotube is attached in aprotruding fashion and a holder are caused to approach very closely toeach other, so that the base end portion of the nanotube is caused toadhere to the holder surface in a state in which the tip end portion ofthe nanotube is caused to protrude, and a third process in which thebase end portion of the nanotube is fused to the holder by irradiationwith an electron beam.

The present invention provides a surface signal operating probe and amethod for manufacturing the same, in which the nanotube is a carbonnanotube, BCN type nanotube or BN type nanotube.

The term “electronic device” used in the present invention refers to anelectronic device that uses a probe for the operation of surfacesignals. For examples, such electronic devices include scanning probemicroscopes; these are devices that image the arrangement of surfaceatoms of a sample using a probe. Furthermore, such electronic devicesalso include magnetic information processing devices; for example,magnetic disk drives such as hard disks, etc., input and output magneticinformation using a magnetic head as a probe. Accordingly, the surfacesignal operating probe of the present invention includes not only casesin which conditions or signals of the opposite surface are detected, butalso cases in which signals are exchanged with the opposite surface.

Below, the present invention will be described in detail using mainly ascanning probe microscope as the electronic device of the presentinvention.

The term “scanning probe microscope” refers to a microscope whichdetects physical and chemical actions from the atoms of the samplesurface by means of the probe needle of a probe, and develops an imageof the sample surface from such detection signals while scanning theprobe needle over the surface of the sample. The probe needle is asensor which detects physical and chemical actions; the probe refers toa device to which the probe needle is attached. The structure of theprobe varies according to the types of physical and chemical actionsdetected, i.e., according to the type of microscope. However, what iscommon to all such probes is a fine probe needle and a probe needleholder to which this probe needle is integrally fastened. In the presentinvention, a nanotube is used as the probe needle.

Scanning probe microscopes include scanning tunnel microscopes (STM)which detect a tunnel current, atomic force microscopes (AFM) whichdetect surface indentations and projections using the van der Waalsforce, leveling force microscopes (LFM) which detect surface differencesby means of frictional force, magnetic force microscopes (MFM) whichdetect magnetic interactions between a magnetic probe needle andmagnetic field regions on the sample surface, electric field forcemicroscopes (EFM) which apply a voltage across the sample and probeneedle, and detect the electric field force gradient, and chemical forcemicroscopes (CFM) which image the surface distribution of chemicalfunctional groups, etc. What these microscopes have in common is thatthey all detect characteristic physical or chemical actions by means ofa probe needle, and thus attempt to detect surface information with ahigh resolution at the atomic level.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a structural diagram of a scanning tunnel microscope (STM).

FIG. 2 is a structural diagram of an atomic force microscope (AFM).

FIG. 3 shows perspective views of various tip end shapes of carbonnanotubes (CNT).

FIG. 4 is a perspective view illustrating one example of the arrangementof five-member rings and six-member rings in a CNT.

FIG. 5 is a structural diagram illustrating one example of a DCelectrophoresis method.

FIG. 6 is a structural diagram illustrating one example of an ACelectrophoresis method.

FIG. 7 is a schematic diagram showing states of adhesion of nanotubes toa knife edge.

FIG. 8 is a computer image of a scanning electron microscope image of aknife edge with an adhering CNT.

FIG. 9 is a computer image of a scanning electron microscope imageshowing a CNT prior to the pressing of this CNT by means of a memberwith a sharp tip.

FIG. 10 is a computer image of a scanning electron microscope imageshowing a CNT immediately after this CNT has been pressed by means of amember with a sharp tip, wherein the CNT is bent.

FIG. 11 is a structural diagram of a device used to transfer a nanotubeto the cantilever of an AFM.

FIG. 12 is a layout diagram showing the state immediately prior to thetransfer of the nanotube in Embodiment 1.

FIG. 13 is a layout diagram showing the state immediately following thetransfer of the nanotube.

FIG. 14 is a layout diagram showing the formation of a coating filmcovering the nanotube.

FIG. 15 is a computer image of a scanning electron microscope image of acompleted AFM probe.

FIG. 16 is a computer image of a DNA image picked up by the completedAFM probe.

FIG. 17 is a layout diagram showing a case in which a coating film isalso formed on an intermediate part constituting a region on the baseend side of the tip end portion of the nanotube (as Embodiment 2).

FIG. 18 is a perspective view which shows the essential parts of an STMprobe as Embodiment 3.

FIG. 19 is a layout diagram which shows the state immediately prior tothe fusion-welding of the nanotube in Embodiment 5.

FIG. 20 is a layout diagram which shows the state immediately followingthe fusion-welding of the nanotube.

FIG. 21 is a schematic diagram of a completed AFM probe.

FIG. 22 is a schematic diagram showing the forming of a coating filmcovering the nanotube in Embodiment 7.

FIG. 23 is a perspective view which shows essential parts of an STMprobe as Embodiment 8.

FIG. 24 is a perspective view which shows essential parts of an STMprobe in a case where a coating film is formed on an intermediate partconstituting a region on the base end side of the tip end portion of thenanotube, as Embodiment 9.

FIG. 25 is a schematic diagram of a conventional electrolytic polishingapparatus.

FIG. 26 is a diagram showing the completion of electrolytic polishing.

FIG. 27 is a schematic diagram of a conventional AFM probe needle.

FIG. 28 is a process diagram showing a semiconductor planar techniquefor a conventional AFM probe needle.

BEST MODE FOR CARRYING OUT THE INVENTION

In order to describe the present invention in greater detail, theinvention will be described with reference to the accompanying drawings.

FIG. 1 is a structural diagram of a scanning tunnel microscope (STM) towhich the present invention is applied. The nanotube probe needle 1 isfastened to a holder 2 a to form a detection probe 2. The method offastening will be described later. This holder 2 a is inserted into thecut groove 3 a of a holder setting part 3, and is fastened in place bymeans of spring pressure so that the holder 2 a can be detached. Ascanning driving part 4 comprises an X piezo-electric element 4 x, a Ypiezo-electric element 4 y and a Z piezo-electric element 4 z scans theholder setting part 3 by expanding and contracting in the X, Y and Zdirections, and thus causes scanning of the nanotube probe needle 1relative to the sample 5. The reference numeral 6 is a bias powersupply, 7 is a tunnel current detection circuit, 8 is a Z-axis controlcircuit, 9 is an STM display device, and 10 is an XY scanning circuit.

The Z axis control circuit controls the nanotube probe needle 1 byexpansion and contraction in the Z direction so that the tunnel currentremains constant at each XY position. This amount of movementcorresponds to the amount of indentation or projection in the Z axisdirection. As the nanotube probe needle 1 is scanned in the X and Ydirections, a surface-atomic image of the sample 5 is displayed by theSTM display device. When the nanotube probe needle 1 is replaced in thepresent invention, the holder 2 a is removed from the holder settingpart 3, and the probe 2 is replaced as a unit.

FIG. 2 is a structural diagram of an atomic force microscope (AFM) towhich the present invention is applied. The nanotube probe needle 1 isfastened to a holder 2 a. The holder 2 a is a pyramid-form member formedon the tip end of a cantilever 2 b. The cross section of this pyramid isa right-angled triangle, and the probe needle 1 is fastened to theperpendicular surface; accordingly, the probe needle 1 contacts thesample surface more or less perpendicularly, so that the shape of thesample surface can be accurately read. The cantilever 2 b is fastened toa substrate 2 c and fastened in a detachable manner to a holder settingpart (not shown). In this configuration, the nanotube probe needle 1,holder 2 a, cantilever 2 b and substrate 2 c together constitute theprobe 2; when the probe needle is replaced, the entire probe 2 isreplaced. For example, if the conventional pyramid-form probe needle 87shown in FIG. 27 is utilized as the holder 2 a, the nanotube probeneedle can be fastened to this by a method described later. The sample 5is driven in the X, Y and Z directions by a scanning driving part whichis a piezo-electric element. 11 indicates a semiconductor laser device,12 indicates a reflective mirror, 13 indicates a two-part split lightdetector, 14 indicates an XYZ scanning circuit, 15 indicates an AFMdisplay device, and 16 indicates a Z axis detection circuit.

The sample 5 is caused to approach the nanotube probe needle 1 in thedirection of the Z axis until the sample 5 is in a position where aspecified repulsive force is exerted; and afterward, the scanningdriving part 4 is scanned in the X and Y directions by the scanningcircuit 14 with the Z position in a fixed state. In this case, thecantilever 2 b is caused to bend by the indentations and projections ofthe surface atoms, so that the reflected laser beam LB enters thetwo-part split light detector 13 after undergoing a positionaldisplacement. The amount of displacement in the direction of the Z axisis calculated by the Z axis detection circuit 16 from the difference inthe amounts of light detected by the upper and lower detectors 13 a and13 b, and an image of the surface atoms is displayed by the AFM displaydevice 15 with this amount of displacement as the amount of indentationand projection of the atoms. This device is constructed so that thesample 5 is scanned in the X, Y and Z directions. However, it is alsopossible to scan the probe needle side, i.e., the probe 2, in the X, Yand Z directions. The nanotube probe needle 1 may be caused to vibrateso that it lightly strikes the surface of the sample 5.

The nanotube probe needle 1 shown in FIGS. 1 and 2 is a nanotube itself,such as a carbon nanotube, BCN type nanotube or BN type nanotube, etc.Of these various types of nanotubes, the carbon nanotube (also referredto as “CNT” below) was discovered first. In the past, diamond, graphiteand amorphous carbon have been known as stable allotropes of carbon. Thestructures of these allotropes were also in states that were more orless determined by X-ray analysis, etc. In 1985, however, fullerene, inwhich carbon atoms are arranged in the form of a soccer ball, wasdiscovered in a vapor cooled product obtained by irradiating graphitewith a high-energy laser, and this compound was expressed as C₆₀. In1991, furthermore, carbon nanotubes, in which carbon atoms are arrangedin a tubular form, were discovered in a cathodic deposit produced bymeans of a DC arc discharge.

BCN type nanotubes were synthesized on the basis of the discovery ofsuch carbon nanotubes. For example, a mixed powder of amorphous boronand graphite is packed into a graphite rod, and is evaporated innitrogen gas. Alternatively, a sintered BN rod is packed into a graphiterod, and is evaporated in helium gas. Furthermore, an arc discharge maybe performed in helium gas with BC₄N used as the anode and graphite usedas the cathode. BCN type nanotubes in which some of the C atoms in acarbon nanotube are replaced by B atoms and N atoms have beensynthesized by these methods, and multi-layer nanotubes in which BNlayers and C layers are laminated in a concentric configuration havebeen synthesized.

Very recently, furthermore, BN type nanotubes have been synthesized.These are nanotubes which contain almost no C atoms. For example, acarbon nanotube and powdered B₂O₃ are placed in a crucible and heated innitrogen gas. As a result, the carbon nanotube can be converted into aBN type nanotube in which almost all of the C atoms of the carbonnanotube are replaced by B atoms and N atoms.

Accordingly, not only carbon nanotubes, but also general nanotubes suchas BCN type nanotubes or BN type nanotubes, etc., can be used as thenanotubes of the present invention.

Since these nanotubes have more or less the same substance structure ascarbon nanotubes, carbon nanotubes will be used as an example in thestructural description below.

Carbon nanotubes (CNT) is a cylindrical carbon substance with aquasi-one-dimensional structure which has a diameter of approximately 1nm to several tens of nanometers, and a length of several microns.Carbon nanotubes of various shapes, as shown in FIG. 3, have beenconfirmed from transmission electron micrographs. In the case of FIG.3(a), the tip end is closed by a polyhedron, while in the case of FIG.3(b), the tip end is open. In the case of FIG. 3(c), the tip end isclosed by a conical shape, while in the case of FIG. 3(c), the tip endis closed by a beak shape. In addition, half-donut type nanotubes arealso known to exist.

It is known that the atomic arrangement of a carbon nanotube is acylinder which has a helical structure formed by shifting and rolling upa graphite sheet. It is known that the end surface of the cylinder of aCNT can be closed by inserting six five-member rings. The fact thatthere are diverse tip end shapes as shown in FIG. 3 is attributable tothe fact that five-member rings can be arranged in various ways. FIG. 4shows one example of the tip end structure of a carbon nanotube; it isseen that this structure varies from a flat plane to a curved surface asa result of six-member rings being arranged around a five-member ring,and that the tip end has a closed structure. Circles indicate carbonatoms, solid lines indicate the front side, and dotted lines indicatethe back side. Since there are various possible arrangements offive-member rings, the tip end structures show diversity.

Not only carbon nanotubes, but also general nanotubes show such a tubestructure. Accordingly, nanotubes show an extremely strong rigidity inthe central axial direction and in the bending direction; and at thesame time, like other carbon allotropes, etc., nanotubes show extremechemical and thermal stability. Accordingly, when nanotubes are used asprobe needles, these nanotubes tend not to be damaged even if theycollide with atomic projections on the sample surface during scanning.Furthermore, since the cross-sectional diameters of nanotubes aredistributed over a range of approximately 1 nm to several tens ofnanometers (as described above), such nanotubes are most suitable asmaterials of probe needles which can produce sharp images of finestructures at the atomic level (if a nanotube with a small curvatureradius is selected). Furthermore, since there are many nanotubes thathave conductivity, nanotubes can be utilized not only as AFM probeneedles, but also as STM probe needles. Furthermore, since nanotubes aredifficult to break, they can also be used as probe needles in otherscanning probe microscopes such as leveling force microscopes, etc.

Among nanotubes, carbon nanotubes are especially easy to manufacture,and are suited to inexpensive mass production. It is known that carbonnanotubes are produced in the cathodic deposit of an arc discharge.Furthermore, such carbon nanotubes are generally multi-layer tubes.Furthermore, it has been found that single-layer carbon nanotubes areobtained when the arc discharge method is modified and a catalytic metalis mixed with the anode. Besides the arc discharge method, carbonnanotubes can also be synthesized by CVD using fine particles of acatalytic metal such as nickel or cobalt, etc., as a substrate material.Furthermore, it is also known that single-layer carbon nanotubes can besynthesized by irradiating graphite containing a catalytic metal withhigh-output laser light at a high temperature. Furthermore, it has alsobeen found that such carbon nanotubes include nanotubes that envelop ametal.

Moreover, as described above, it has been found that BCN type nanotubesand BN type nanotubes, etc., can also be inexpensively manufacturedusing an arc discharge process or crucible heating process, etc., andtechniques for enveloping metals in nanotubes are also being developed.

However, for example, in the carbon nanotube manufacturing process, itis known that carbon nanotubes are not produced just by themselves;instead, such nanotubes are produced in a mixture with large quantitiesof carbon nanoparticles (hereafter also abbreviated to “CP”).Accordingly, the recovery of CNT from this mixture at a high density isa prerequisite for the present invention.

In regard to this point, the present inventors have already provided aCNT purification method and purification apparatus based on anelectrophoretic process in Japanese Patent Application No. 10-280431. Inthis method, CNTs can be purified by dispersing the carbon mixture in anelectrophoretic solution, and applying a DC voltage or AC voltage. Forexample, if a DC voltage is applied, the CNTs are arranged in straightrows on the cathode. If an AC voltage is applied, the CNTs are arrangedin straight rows on both electrodes as a result of the formation of anon-uniform electric field. Since the degree of electrophoresis of CPsis smaller than that of CNTs, CNTs can be purified by means of anelectrophoretic process utilizing this difference.

It has been confirmed that this electrophoretic method can be used topurify not only carbon nanotubes, but also BCN type nanotubes and BNtype nanotubes.

This electrophoretic method is also used in the working of the presentinvention. Specifically, nanotubes purified and recovered by theabove-described method are dispersed in a separate clean electrophoreticsolution. When metal plates such as knife edges, etc., are positionedfacing each other as electrodes in this solution, and a DC voltage isapplied to these electrodes, nanotubes adhere to the cathode (forexample) in a perpendicular configuration. If the electrodes arepositioned so that a non-uniform electric field is formed in cases wherean AC voltage is applied, nanotubes will adhere to both electrodes in aperpendicular configuration. These electrodes with adhering nanotubesare utilized in the manufacturing process of the present invention. Ofcourse, other methods of causing nanotubes to adhere to aknife-edge-form metal plate may also be used.

The above-described electrophoretic solution may be any solution that iscapable of dispersing the nanotubes so that the nanotubes undergoelectrophoresis. Specifically, the solvent used is a dispersing liquid,and is at the same time an electrophoretic liquid. Solvents which can beused in this case include aqueous solvents, organic solvents and mixedsolvents consisting of both types of solvents. For example, universallyknown solvents such as water, acidic solutions, alkaline solutions,alcohol, ethers, petroleum ethers, benzene, ethyl acetate andchloroform, etc., may be used. More concretely, all-purpose organicsolvents such as isopropyl alcohol (IPA), ethyl alcohol, acetone andtoluene, etc., may be utilized. For example, in the case of IPA,carboxyl groups are present as electrophoretic ion species. Thus, it isadvisable to select the solvent used on the basis of a comprehensiveevaluation of the electrophoretic performance and dispersion performanceof the nanotubes, the stability of the dispersion, and safety, etc.

FIG. 5 shows a case involving CNTs as one example of a DCelectrophoretic process. The electrophoretic solution 20 in which theCNTs are dispersed is held inside a hole formed in a glass substrate 21.Knife edges 22 and 23 are positioned facing each other in the solution,and a DC power supply 18 is applied. Although not visible to the nakedeye, countless extremely small carbon nanotubes (CNTs) are present inthe electrophoretic solution. These CNTs adhere in a perpendicularconfiguration to the tip end edge 22 a of the cathode knife edge 22.This can be confirmed under an electron microscope. In this apparatus, anon-uniform electric field in which the lines of electric force are bentin the direction perpendicular to the plane of the knife edges is formedbetween the two electrodes. However, this can be utilized as a DCelectrophoresis apparatus even if a uniform electric field is formed.The reason for this is as follows: specifically, in the case of anon-uniform electric field, the rate of electrophoresis is merelynon-uniform; electrophoresis is still possible.

FIG. 6 shows a case involving CNTs as one example of an ACelectrophoretic process. The electrophoretic solution 20 in which theCNTs are dispersed is held inside a hole formed in a glass substrate 21.Knife edges 22 and 23 are positioned facing each other in the solution,and an AC power supply 19 is applied via an amplifier 26. A non-uniformelectric field similar to that of FIG. 5 acts between the electrodes.Even if a non-uniform electric field is not intentionally constructed,local non-uniform electric fields are actually formed, so thatelectrophoresis can be realized. In this figure, a 5 MHz, 90 Valternating current is applied. CNTs adhere in a perpendicularconfiguration to the tip end edges 22 a and 23 a of the knife edges ofboth electrodes.

FIG. 7 is a schematic diagram showing states of adhesion of nanotubes 24to the tip end edge 23 a of a knife edge 23. The nanotubes 24 adhere tothe tip end edge 23 a in a more or less perpendicular configuration, butsome of the nanotubes are inclined. Furthermore, there are also cases inwhich a plurality of nanotubes are gathered together so that they adherein the form of bundles; these are referred to as NT bundles 25 (alsocalled nanotube bundles). The curvature radii of the nanotubes aredistributed over a range of approximately 1 nm to several tens ofnanometers. In cases where excessively slender nanotubes are selected asprobe needles, such probe needles offer the advantage of allowing fineobservation of indentations and projections in the atomic surface;conversely, however, such nanotubes may begin to vibrate in acharacteristic mode, and in such cases, the resolution drops. Here, ifan NT bundle 25 is used as a probe needle, the nanotube that protrudesthe furthest forward in this bundle fulfils the function of a directprobe needle, while the other nanotubes act to suppress vibration.Accordingly, such NT bundles 25 can also be used as probe needles.

FIG. 8 is a computer image of a scanning electron microscope image of aknife edge with an adhering CNT. It is seen that CNTs can easily becaused to adhere to a knife edge merely by performing an electrophoreticoperation. However, CNTs more commonly adhere to the tip end edge at aninclination rather than at right angles.

The knife edge shown in FIG. 8 is subjected to a special treatment forthe purpose of a strength test. This electron-microscopic apparatuscontains considerable quantities of organic substances as impurities.Accordingly, it was found that when this knife edge is irradiated withan electron beam, a carbon film originating in the impurities is formedon the surface of the knife edge. The details of this phenomenon will bedescribed later; however, this carbon film is formed on the knife edgesurface so that it covers only some of the CNTs. In other words, thecarbon film has the function of fastening CNTs to the knife edge thatwere merely adhering to the knife edge. Other nanotubes besides CNTs canbe similarly treated.

The mechanical strength of CNTs on the above-described knife edge wastested. The CNTs were pressed by a member with a sharpened tip. FIGS. 9and 10 show computer images of scanning electron microscope imagesobtained before and after pressing. As is clearly seen from FIG. 10, theCNT has a bending elasticity which is such that there is no breakage ofthe CNT even when the CNT is bent into a semicircular shape. Whenpressing was stopped, the CNT returned to the state shown in FIG. 9.Such a high strength and high elasticity are the reason why CNTs are notdamaged even if they contact the atomic surface or are dragged acrossthe atomic surface. This also verifies that the carbon film stronglyfastens the CNTs in place. Thus, the fastening force is sufficient sothat the CNTs are not separated from the knife edge even if bent.General nanotubes also have such a high strength and high elasticity;this is a major advantage of using nanotubes as probe needles.

FIG. 11 is a diagram of a device used to transfer a nanotube to thecantilever of an AFM holder. A holder 2 a is caused to protrude in theform of a pyramid from the tip end of a cantilever 2 b. This is a membermade of silicon which is manufactured using a semiconductor planartechnique. Ordinarily, such a pyramid-form protruding part is used as anAFM. However, in the present invention, this pyramid-form protrudingpart is converted to use as a holder 2 a. A nanotube 24 on the knifeedge 23 is transferred to this holder 2 a, and this nanotube 24 is usedas a probe needle. Since the nanotubes on the knife edge are merelyadhering to the knife edge, they are naturally not fastened by a film.These operations are preformed under real-time observation inside ascanning electron microscope chamber 27. The cantilever 2 b can be movedthree-dimensionally in the X, Y and Z directions, and the knife edge canbe move two-dimensionally in the X and Y directions. Accordingly,extremely minute operations are possible.

The surface signal operating probe of the present invention is completedby transferring a nanotube adhering to the knife edge to a holder, andfastening this nanotube to the holder by a fastening means. In regard tothis fastening means, two methods are used in the present invention. Oneis a coating film; in this case, the nanotube is fastened to the holderby means of a coating film. The second method uses a fusion-welded part;in this case, the nanotube is caused to adhere to the holder, and thecontact portion is fused so that the two members are bonded to eachother. Since nanotubes are extremely slender, the entire base endportion of the nanotube in contact with the holder tends to form thefusion-welded part. Fusion welding methods include fusion welding bymeans of an electric current and fusion welding by electron beamirradiation.

Below, concrete examples of nanotube fastening means will be describedas embodiments.

Embodiment 1

[AFM Probe Fastened by a Coating Film]

FIG. 12 is a layout diagram showing the state immediately prior to thetransfer of the nanotube. While being observed under an electronmicroscope, the tip end of the holder 2 a is caused to approach veryclose to the nanotube 24. The holder 2 a is positioned so that thenanotube 24 is divided into a tip end portion length L and base endportion length B by the tip end of the holder 2 a. Furthermore, atransfer DC power supply 28 is provided in order to promote thistransfer, and the cantilever 2 b is set on the cathode side. However,the polarity of the DC power supply also depends on the material of thenanotube; accordingly, the polarity is adjusted to the direction thatpromotes transfer. The transfer of the nanotube is promoted when thisvoltage is applied. A voltage of several volts to several tens of voltsis sufficient. This voltage can be varied according to the transferconditions. Furthermore, this power supply 28 may also be omitted. Whenthe approach distance D becomes closer than a specified distance, anattractive force acts on both members, so that the nanotube 24spontaneously jumps to the holder 2 a. As the approach distance Dbecomes closer, the actual values of the lengths L and B approach thepreset design values. This transfer may include cases in which thenanotube 24 contacts both the knife edge 23 and holder 2 a; and thesemay be separated following the formation of the coating film.

FIG. 13 is a layout diagram showing the state in which the nanotube 24adheres to the holder 2 a. The tip end portion 24 a protrudes by the tipend portion length L, and the base end portion 24 b adheres to theholder 2 a by the base end portion length B. The tip end portion 24 aconstitutes the probe needle. It would also be possible to cause an NTbundle 25 to adhere to the holder instead of a single nanotube 24.Furthermore, if single nanotubes 24 are transferred and caused to adhereto the holder a number of times, an effect which is the same as causingan NT bundle 25 to adhere to the holder can be obtained. In cases wherenanotubes are caused to adhere a number of times, the individualnanotubes can be caused to adhere after being arbitrarily adjusted.Accordingly, a stable, high-resolution probe can be manufactured inwhich the nanotube that protrudes furthest to the front acts as theprobe needle, while the surrounding nanotubes suppress resonance of theprobe needle as a whole.

Next, a coating film is formed over a specified region including thebase end portion 24 b of the nanotube 24, so that the nanotube 24 isfirmly fastened to the holder 2 a. As seen from FIG. 14, the coatingfilm 29 is formed so that it covers the base end portion 24 a fromabove. As a result of this coating film 29, even if the tip end portion24 a constituting the probe needle should catch on an atomic projection,the probe needle will merely flex into a bent state as described above.Thus, damage such as breakage of the probe needle or removal of theprobe needle from the holder 2 a can be prevented. If this coating film29 is absent, the nanotube 24 will separate from the holder 2 a when thetip end portion 24 a catches on a projection.

Next, methods which can be used to form the coating film 29 will bedescribed. As described above, one method which can be used is asfollows: specifically, when the base end portion 24 b is irradiated withan electron beam, carbon substances floating inside the electronmicroscope chamber 27 are deposited in the vicinity of the base endportion so that a carbon film is formed. This carbon film is used as acoating film. A second method is a method in which a very small amountof a reactive coating gas is introduced into the electron microscopechamber 27, and this gas is decomposed by means of an electron beam, sothat a coating film of the desired substance is formed. In addition,general coating methods can also be employed. For example, CVD (alsoreferred to as chemical vapor deposition) and PVD (also referred to asphysical vapor deposition) can be utilized. In the case of a CVDprocess, the material is heated beforehand, and a reactive coating gasis caused to flow to this location, so that a coating film is reactivelygrown on the surface of the material. Furthermore, the low-temperatureplasma method in which the reaction gas is converted into a plasma and acoating film is formed on the surface of the material is also one typeof CVD method. Meanwhile, PVD methods include several types of methodsranging from simple vapor deposition methods to ion plating methods andsputtering methods, etc. These methods can be selectively used in thepresent invention, and can be widely used on coating film materialsranging from insulating materials to conductive materials in accordancewith the application involved.

FIG. 15 is a scanning electron microscope image of a completed probe. Itis seen that a CNT is fastened to the holder in accordance with thedesign. The present inventors took AFM images of deoxyribonucleic acid(DNA) in order to measure the resolution and stability of this probe.FIG. 16 shows an AFM image of this DNA; and the crossing and twining ofthe DNA were clearly imaged. To the best knowledge of the inventors,this is the first time that such clear DNA images have been obtained.Judging from FIG. 16, it appears that the tip end curvature radius ofthis probe constructed according to the present invention is 1.2 nm orless; it will be understood that this is extremely effective inscientific research.

Embodiment 2

[Reinforced AFM Probe Fastened by Coating Film]

FIG. 17 shows another coating film formation method. In order to obtainhigh-resolution images, it is desirable that the curvature radius of thetip end of the nanotube 24 be small. However, as described above, thereare cases in which the tip end portion undergoes microscopic vibrationsif the nanotube is too slender, so that the images become blurred.Accordingly, in cases where a slender nanotube 24 is used, a coatingfilm 30 is also formed on a region of the tip end portion 24 a that isclose to the base end portion 24 b, i.e., on an intermediate portion 24c. As a result of this coating film 30, the intermediate portion 24 c ismade thicker and greater in diameter, so that an effect that suppressesmicroscopic vibrations is obtained. This coating film 30 may be formedfrom the same material as the coating film 29 at the same time that thecoating film 29 is formed, or may be formed from a different material.In this way, a probe needle comprising a single nanotube in which thetip end of the nanotube 24 is slender and the root of the nanotube isthick can be constructed. In other words, a high-resolution,high-reliability probe needle can be constructed from a slendernanotube, without using an NT bundle 25.

Embodiment 3

[STM Probe Fastened by Coating Film]

FIG. 18 is a perspective view of the essential parts of a scanningtunnel microscope probe 2. The tip end portion 24 a of a nanotube 24 iscaused to protrude, and this portion constitutes the probe needle. Thebase end portion 24 b is fastened to a holder 2 a by means of a coatingfilm 29. This probe may be easily understood by a comparison with theprobe 2 in FIG. 1. The actions and effects of this probe are similar tothose of Embodiment 1; accordingly, a detailed description is omitted.

Embodiment 4

[Magnetic Probe Fastened by Coating Film]

A probe similar to that shown in FIG. 18 can be utilized as aninput-output probe in a magnetic disk drive. In this case, iron atomsare embedded in the tip end of the nanotube, so that the nanotube isendowed with a magnetic effect. Since a nanotube has a tubularstructure, various types of atoms can be contained inside the tube.Among these atoms, magnetic atoms can be contained in the tube, so thatthe nanotube is endowed with magnetic sensitivity. Of course,ferromagnetic atoms other than iron atoms may also be used. Since thetip end curvature radius of a nanotube is extremely small, i.e., a valueranging from approximately 1 nm to several tens of nanometers, the inputand output of data recorded at a high density in an extremely smallspace can be performed with high precision.

Embodiment 5

[AFM Probe Fastened by Electric Current Fusion Welding]

FIGS. 19 through 24 illustrate an embodiment of fusion-welding fasteningof the nanotube. First, FIG. 19 is a layout diagram of the stateimmediately prior to fusion welding of the nanotube. The tip end of theholder 2 a is caused to approach very closely to the nanotube 24 whilebeing observed under an electron microscope. The holder 2 a ispositioned so that the nanotube 24 is divided into a tip end portionlength L and base end portion length B by the tip end of the holder 2 a.Furthermore, a high resistance R, a DC power supply 28 and a switch SWare connected between the knife edge 23 and cantilever 2 b. For example,the resistance value of the high resistance R is 200 MΩ, and the voltageof the DC power supply is 1 to 100 V. In FIG. 19, in which the membersare in a close proximity, the switch SW is in an open state, and nocurrent has yet been caused to flow.

When the two members are caused to approach each other even more closelyso that the nanotube 24 contacts the holder 2 a, the state shown in FIG.20 results. Here, the tip end portion 24 a protrudes by an amount equalto the tip end portion length L, and the base end portion 24 b adheresto the holder 2 a for a length equal to the base end portion length B.When the switch SW is closed so that current flows in this stage,current flows between the nanotube 24 and the holder 2 a, so that thebase end portion 24 b that is in contact with the holder 2 a isfusion-welded to the holder 2 a by current heating. In other words, thebase end portion 24 b is fused to form the fusion-welded part 24 dindicated by a black color in the figure, and the nanotube 24 is firmlyfastened to the holder 2 a.

It is also possible to use a process in which the switch SW is closedprior to the contact between the nanotube 24 and the holder 2 a, afterwhich the base end portion 24 b is converted into the fusion-welded part24 d by the flow of current caused by contact, and then the holder 2 ais moved away from the knife edge 23.

In this electric current fusion welding treatment, not only is thefastening strong, but fusion welding can be reliably performed with thefeeling of spot welding while confirming the object in the electronmicroscope, so that the product yield is increased. The DC power supply28 may be replaced by an AC power supply or pulsed power supply. In thecase of a DC power supply, fusion welding can be performed using acurrent of 10⁻¹⁰ to 10⁻⁶ (ampere-seconds (A·s)). For example, in a casewhere the diameter of the carbon nanotube (CNT) is 10 nm, and the lengthB of the base end portion is 200 nm, stable fusion welding can beperformed at 10⁻⁹ to 10⁻⁷ (A·s). However, the gist of the presentinvention lies in the fastening of the CNT by fusion welding, and thepresent invention is not limited to these numerical values.

Embodiment 6

[AFM Probe Fastened by Electron Beam Fusion Welding]

The second fusion welding method is the electron beam irradiationmethod. When the switch SW is closed in the non-contact state shown inFIG. 19, an electric field is formed between the holder 2 a and thenanotube 24. When the respective members are caused to approach eachother even more closely, the nanotube 24 is caused to fly onto theholder 2 a by the force of this electric field. Afterward, when all orpart of the base end portion 24 b of the nanotube 24 is irradiated withan electron beam, the base end portion 24 b melts and is fusion-weldedto the holder 2 a as the fusion-welded part 24 d.

In this case, the polarity of the DC power supply 28 depends on thematerial of the nanotube, etc. Thus, this polarity is not limited to thearrangement shown in the drawings; and the polarity is adjusted to thedirection that promotes transfer.

An electric field transfer method is used in the above-described method;however, it is also possible to perform a non-electric-field transferwith the switch SW open. Specifically, when the holder 2 a is caused toapproach the nanotube 24 within a certain distance, a van der Waalsattractive force acts between the two members, and the nanotube 24 iscaused to fly onto the holder 2 a by this attractive force. The surfaceof the holder 2 a may be coated with an adhesive agent such as anacrylic type adhesive agent, etc., in order to facilitate this transfer.Following this transfer, the base end portion 24 b adhering to theholder 2 a is fused by irradiation with an electron beam, so that thenanotube 24 is fastened to the holder 2 a via a fusion-welded part 24 d.Thus, a probe similar to that obtained by current fusion welding canalso be obtained by electron beam fusion welding.

FIG. 21 is a schematic diagram of the completed probe following fusionwelding. The tip end portion 24 a constitutes the nanotube probe needleand can be used as a high-resolution probe with a tip end curvatureradius of 10 nm or less. The nanotube 24 is firmly fastened to theholder 2 a by means of the fusion-welded part 24 d, so that the nanotube24 does not break, bend or come loose even if subjected to aconsiderable impact. In the case of a carbon nanotube, it appears thatthe nanotube structure is destroyed and changed in amorphous carbon inthe fusion-welded part 24 d. If silicon is used as the material of theholder 2 a, it appears that the carbon atoms that have been convertedinto an amorphous substance and the silicon atoms of the holder bond toform silicon carbide, so that the fusion-welded part 24 d assumes asilicon carbide structure. However, detailed structural analysis of thispart has not yet been completed, and this is merely conjecture at thispoint.

In the case of BCN type nanotubes or BN type nanotubes, structuralanalysis of the fusion-welded part has not yet been performed. However,it has been experimentally confirmed that the members are stronglybonded by this fusion-welded part.

As described above, in cases where the holder 2 a is made of silicon,the holder 2 a has a certain amount of conductivity since it is asemiconductor. Accordingly, since a voltage can be directly applied,current fusion welding is possible. Of course, the van der Waalstransfer method or electron beam fusion welding method can also be used.However, in cases where the holder 2 a is constructed from an insulatorsuch as silicon nitride, the holder 2 a has no conductivity. In suchcases, therefore, the transfer method using the van der Waals attractiveforce or the electron beam fusion welding method is the optimal method.In cases where the current fusion welding method cannot be applied to aninsulator, the following procedure may be used: An electrode is formedfrom a conductive substance on the surface of the CNT holder 2 a orcantilever 2 b. An electrode film is formed by means of, for instance,metal vapor deposition, etc. A voltage is applied to this film,resulting in that an electric current flows, the fusion weldingphenomenon occurs, and a probe is thus obtained.

Embodiment 7

[AFM Probe Fastened by Coating Film and Fusion Welding]

In cases where a single nanotube 24 is used as a probe needle, if thetip end portion 24 a of the nanotube is long and slender, it couldhappen that resonance occurs so that the tip end vibrates, thus causinga drop in resolution. In order to suppress such resonance, there is amethod in which an additional coating film is formed on specifiedregions. As is clear from FIG. 22, if a coating film 30 is formed on theroot side of the tip end portion 24 a, this portion becomes thicker sothat resonance tends not to occur. This coating region can be freelydesigned; accordingly, a coating film 29 which extends to the base endportion 24 b may be formed. This coating film 29 has the effect ofpressing the nanotube from above. Thus, together with the fusion-weldedpart 24 d, the coating film reinforces the fastening of the nanotube 24to the holder 2 a. The thickness of the coating films 29 and 30 may bevaried depending upon the case.

Next, methods for forming the coating films 29 and 30 will be described.As described above, in one method, when the base end portion 24 b andintermediate portion 24 c are irradiated with an electron beam, not onlydo these portions melt, but carbon substances floating inside theelectron microscope chamber 27 are deposited in the vicinity of the baseend portion so that a carbon film is formed. This carbon film can beutilized as a coating film. In another method, a trace amount of areactive coating gas is introduced into the electron microscope chamber27, and this gas is broken down by an electron beam, so that a coatingfilm of the desired substance is formed. In addition, general coatingmethods can also be employed. For example, the CVD (also called chemicalvapor deposition) or PVD (also called physical vapor deposition) can besimilarly utilized. Details of these methods are omitted here.

It is also possible to fusion-weld an NT bundle 25 instead offusion-welding a single nanotube 24. If a plurality of nanotubes 24 arefusion-welded one by one, the same effect as the fusion welding of an NTbundle 25 can be obtained. In cases where such fusion welding isperformed one by one, the individual nanotube can be arbitrarilyadjusted and fusion-welded. Accordingly, a stable, high-resolution probecan be obtained in which a nanotube that protrudes furthest forward actsas the probe needle, while the surrounding nanotubes suppress resonanceof the probe needle as a whole.

Embodiment 8

[STM Probe Fastened by Fusion Welding]

FIG. 23 is a perspective view of the essential portion of a scanningtunnel microscope. The tip end portion 24 a of a nanotube 24 is causedto protrude, and this portion acts as a probe needle. The base endportion 24 b forms a fusion-welded part 24 d and is fusion-welded to theholder 2 a. This probe will be easily understood if compared with theprobe 2 shown in FIG. 1. A metal such as tungsten or a platinum-iridiumalloy, etc. can be used as the material of the holder 2 a The actionsand effects of this probe are similar to those of Embodiment 5.Accordingly, details thereof are omitted.

Embodiment 9

[STM Probe Fastened by Coating Film and Fusion Welding]

FIG. 24 shows a probe 2 in which a coating film 30 is formed on theintermediate portion 24 c of the nanotube 24. This coating film 30 isinstalled in order to prevent vibration of the probe needle. As in FIG.22, a coating film 29 which covers the fusion-welded part 24 d may beformed. Since the actions and effects of this probe are similar to thoseof Embodiment 7, details are omitted.

Embodiment 10

[Magnetic Probe Fastened by Fusion Welding]

A probe similar to that shown in FIG. 23 can be utilized as aninput-output probe for a magnetic disk drive. In this case, iron atomsare embedded in the tip end of the nanotube, so that the nanotube isendowed with a magnetic effect. Since a nanotube has a tubularstructure, various types of atoms can be contained inside the tube. Asone example, ferromagnetic items can be contained in the tube, so thatthe nanotube is endowed with magnetic sensitivity. Of course,ferromagnetic atoms other than iron atoms may also be used. Since thetip end curvature radius of a nanotube is extremely small, i.e.,approximately 1 nm to several tens of nanometers, processing such as theinput and output of data recorded at a high density in a very smallspace, etc. can be performed with high precision.

The present invention is not limited to the above-described embodiments;and various modifications and design changes, etc., within limits thatinvolve no departure from the technical spirit of the present inventionare included in the technical scope of the invention.

INDUSTRIAL APPLICABILITY

As described in detail above, the present invention relates to anelectronic device surface signal operating probe which comprises ananotube, a holder which holds this nanotube, and a fastening meanswhich fastens the base end portion of the nanotube to the surface of theholder in a manner that the tip end portion of the nanotube protrude, sothat the tip end portion of the nanotube is used as a probe needle; andit also relates to a method for manufacturing the same. Since a nanotubeis thus used as a probe needle, the tip end curvature radius is small.Accordingly, by way of using this probe needle in a scanning probemicroscope, high-resolution images of surface atoms can be picked up.When this probe needle is used as the probe needle of a magneticinformation processing device, the input and output of high-densitymagnetic information can be controlled with high precision.

Since nanotubes have an extremely high rigidity and bending elasticity,no damage occurs to nanotubes even if they should contact neighboringobjects. Accordingly, the useful life of the probe can be extended.Furthermore, carbon nanotubes are present in large quantities in thecathodic deposits of arc discharges, and other BCN type nanotubes and BNtype nanotubes can easily be manufactured by similar methods.Accordingly, the cost of raw materials is extremely low. In themanufacturing method of the present invention, probes can beinexpensively mass-produced, so that the cost of such probes can belowered, thus stimulating research and economic activity. In particular,STM and AFM probes with a long useful lives that are necessary for thecreation of new substances can be provided inexpensively and in largequantities. Thus, the present invention can contribute to the promotionof technical development.

What is claimed is:
 1. A coated nanotube surface signal probecharacterized in that said probe comprises a nanotube (24), a holder (2a) which holds said nanotube (24), and a coating film (29) fastening abase end portion (24 b) of said nanotube (24) to a surface of saidholder with a tip end portion (24 a) of said nanotube (24) being causedto protrude from said holder (2 a) wherein said probe is assembled bydirect observation in an electron microscope, said coating film isformed by irradiating a base end portion of said nanotube (24) with anelectron beam in said electron microscope so as to fasten said nanotube(24) to said holder (2 a) by said resulting coating film (29), and saidtip end portion (24 a) is used as a probe needle so as to scan surfacesignals.
 2. The coated nanotube surface signal probe according to claim1, wherein said coating film is a carbon film depositing on said baseend portion by said electron beam irradiation.